Electronics Engineer for Smart Grip Prototype

About the project

Smart Grip is a connected hand-grip trainer that measures grip force with a load cell. I need an experienced electronics engineer to take it from a finalized BOM to a tested prototype board: schematic, 4-layer PCB, JLCPCB manufacturing files, and hands-on bring-up of the first boards. This is not a blank-page project. After an NDA you will receive: - System specification and finalized BOM for 11 functional blocks, with LCSC part numbers, stock and price checks - Power budget report: sleep, active and peak current per rail - 49-page engineering test report: 3 load cells tested on a bench with the HX711 (noise, zero drift, linearity, hysteresis, repeatability, dynamic cycling). Result: GO WITH CONDITIONS - Preliminary BOM for the sensor, display, battery and haptic parts - Proof-of-concept firmware on an ESP32-S3 dev board (force, rep counting, touch UI), as reference - External enclosure STEP. A mechanical engineer works in parallel on the internal layout. ARCHITECTURE (already selected) - MCU: ESP32-S3-WROOM-1-N16R8 (PCB antenna, native USB for programming) - Force: 50 kg 4-wire full-bridge load cell -> HX711 on its own LDO rail - Power: USB-C + SRV05-4 ESD -> BQ24075 charger (power path) -> 2x RT9080-33 LDO (digital / analog). No switching regulators. - Battery: 1S Li-Po ~500 mAh, MAX17048 fuel gauge - Display: 1.58" AMOLED 228x460, CO5300 + CST820 touch, 31-pin FPC, QSPI. Wake on touch, no power button. - Haptics: DRV8837 H-bridge + 10 mm coin ERM motor - Connectors: load cell, position sensor (pot or Hall, 3-pin JST PH), battery, motor Still open: load-cell supplier, position sensor part, battery size, final display pick. Their interfaces are fixed, so they do not block the schematic. Main challenge: 1 kg is about 54 µV at the bridge. Grounding, return paths and noise matter more than resolution. MILESTONES (fixed price, please quote each one) M1 Review: read the documents, confirm or challenge the parts with reasons, deliver block diagram, ESP32-S3 pin map, power tree and open questions. M2 Schematic: complete production-intent schematic, ERC clean, datasheet limits checked, BOM with LCSC numbers, test points. M3 PCB: 4-layer layout. Placement first with a STEP file for a mechanical fit check, routing after my approval. Deliver Gerbers, drill, BOM + CPL for JLCPCB assembly, STEP, fab notes. An independent review by a second engineer is a plus. M4 Bring-up: I pay for boards, parts and shipping to you. Test each block with simple test firmware: rails and ripple, charging, fuel gauge, display/touch, haptics, position input, USB programming, sleep current, and HX711 noise while Wi-Fi, display and motor are running. Deliver a report: measured vs expected, issues, severity, fix. M5 Rev B: correct the issues and verify the V2 board. Fixing your own design errors is part of your fee. Changes I request for mechanical reasons are quoted separately. Not included: product firmware, enclosure design, certification. REQUIREMENTS - You have shipped battery-powered boards with an ESP32 module and PCB antenna. Load-cell or other low-level analog experience is a big plus. - KiCad preferred. Native source files and full IP transfer to me. - Your own lab: oscilloscope, bench supply, and a way to measure µA sleep current. IN YOUR BID (bids that skip these will not be read) 1. Start your bid with the word MICROVOLT. 2. Price and days for each milestone M1-M5. 3. 1-2 similar boards you designed (layout screenshots, not only 3D renders). 4. The HX711 and the motor driver share one board. In 2-3 sentences: how would you place and ground them? 5. Which ESP32-S3 ADC would you use for the position sensor, and why? 6. What equipment will you use for bring-up?

Skills required